Studies of a potential in vitro test for estimation of toxicity of aminoglycoside antibiotics and polyamines.

The electrophoretic mobility of phosphatidyl inositol liposomes at pH 7.4, 25 degrees C, was reduced by aminoglycoside antibiotics, neamine and several polyamines in general accordance with the number of amino-groups on each molecule. There was good agreement between the relative position of the tested compounds on the mobility-concentration graph and available information about their relative mammalian toxicities in vivo. The slope of the graph for netilmicin was distinctively flat; a comparatively flat dose-response curve for netilmicin has been reported also from in vivo studies of nephrotoxicity. Investigation of a homologous series of alpha,omega straight chain diaminoalkanes revealed that hydrophobicity did not contribute significantly to the observed interaction in this system. L-Lysine showed the weakest effect amongst all compounds tested, supporting the view that the overall positive charge on the molecule was the major determinant of the observed effect. Further structure-activity work is required to confirm whether this 'in vitro' test is predictive of the toxicity of aminoglycoside antibiotics in man.